LONDON (Reuters) - Lewis Hamilton will start the 200th grand prix of his Formula One career in Belgium this weekend but the triple world champion has smaller but more significant numbers on his mind.

Refreshed from an August break in the Caribbean, including a trip to Cuba in his role as UNICEF ambassador, the Mercedes driver is 14 points behind championship leader Sebastian Vettel as he revs up for the second half of the season.

A fifth victory of 2017 for the Briton would put the pressure back on Ferrari's Vettel and Hamilton can celebrate another milestone by bagging pole position on Saturday at the long and fast Spa-Francorchamps circuit.

That would see Hamilton, who sportingly relinquished third place to team mate Valtteri Bottas in Hungary before the summer shutdown, match the record of 68 poles set by Michael Schumacher with Ferrari in 2006.

Mercedes have won the last two Belgian Grands Prix, with now-retired 2016 world champion Nico Rosberg triumphant from pole last year after Hamilton won in 2015.

Nobody will be taking anything for granted, however, after Ferrari's one-two win in Budapest at the end of July.

"On paper, people will assume that Spa should suit our car because it is a circuit where aerodynamic efficiency is extremely important," Mercedes team boss Toto Wolff said.

"But assumptions are dangerous -- we have seen too many times already this season that the form book can be rewritten from one weekend to the next. So we will be making no assumptions."

Hamilton has won twice before at Spa, as has Vettel, but the track -- a classic blast from the past -- has not been particularly kind to him.

In 2008, when he won his first title, the Briton was demoted from first to third after the race for cutting a chicane, with then Ferrari rival Felipe Massa savouring victory instead.

Spa can often be a lottery, with its capricious weather, and rain could be a boon for Red Bull's Belgian-born Dutch teenager Max Verstappen, who can count on plenty of local support in what amounts to a home race.

"I just love the track and it'll be nice seeing so many orange (Dutch) fans in the grandstands," he said.

"Spa is my favourite track of the year. You have to get everything right but when you get a good lap it's very rewarding."

Belgium could also be good for Ferrari's Kimi Raikkonen, who arrives with a new contract for 2018 in his pocket.

The fearless Finnish 'Iceman' has won four times at Spa but will need to be beyond the reach of Ferrari 'team orders' if he is to do it again.

"For sure there are some circuits that fit us better," Raikkonen, whose last Belgian win in 2009 was also Ferrari's most recent at Spa, said in Hungary.

"The Mercedes has better horsepower but it depends on so many things.

"If you purely look now, you would say it's not going to be as easy for us as here (Hungary) but obviously we try to improve and we are going to do our best."

Sunday's race, the 50th world championship Grand Prix held at Spa, will also see a Belgian competing -- McLaren rookie Stoffel Vandoorne -- for the first time since Jerome d'Ambrosio in 2012.